The use of vacuum bottles, or vacuum-type circuit interrupters is increasing in popularity due to their small size, long operational life, high-current interrupting capability, and short travel of the moving contact, which is required for interruption, usually the contact stroke only requiring one-half inch, or less in travel.
In addition, the tremendous amount of development work, which has been conducted by the several manufacturing companies in regard to the contact materials has considerably reduced the hazard of voltage surges occurring on the line, and increasing tremendously the operational life of the interrupters. Today, vacuum interrupters are a reliable component part of much switchgear apparatus. Their use in many structures is exemplified in various types of equipment. For example, vacuum interrupters may be used in submersible equipment, such as set forth in U.S. Pat. No. 3,582,591, issued June 1, 1971 to Robert A. Few. Additionally, reclosing equipment, utilizing vacuum bottles, is today quite prevalent, as exemplified in U.S. Pat. No. 3,601,565, issued Aug. 24, 1971, by Robert A. Few, and likewise assigned to the assignee of the instant application. For high-voltage equipment, the use of vacuum interrupters in series is utilized extensively. Consider, for example, U.S. Patent application filed Oct. 30, 1970, Ser. No. 085,512, by Richard E. Kane and Frank Reese, and assigned to the assignee of the instant application. Also, vacuum interrupters are used for a diversified number of applications, such as interrupting direct current, as set forth in U.S. Pat. Nos. 3,435,288 -- Greenwood, 3,489,951 -- Greenwood et al, and 3,489,950 -- Mishkovsky.
Regardless of the manner of use, vacuum interrupters have difficulty in dissipating the heat, which is generated interiorly of the evacuated envelope at the engaged contacts in the closed position of the devices. It has been found that contact and stem deformation at room temperature in the vacuum bottles, due to impacts during closing operations have been quite prevalent. This indicates that the strength of the soft copper, used as the contact material, is marginal. In addition, deformation of the contact structures, and a small amount of deformation of the contact-stems has occurred. At any rate, the yield strength of annealed copper can decrease, by as much as 4,000 p.s.i., if the temperature were to increase from room temperature to 195.degree. C. according to standard materials handbooks. Also, the creep rate for annealed 1.125 diameter copper at 204.degree. C. under 850 pounds load, is approximately 0.003 inch/year. It is, therefore, desirable to provide a heat-dissipating means, which may be used to transmit the generated heat at the contacts within the vacuum-bottle envelope to a region externally thereof to suitable heat-dissipating cooling structures, to thereby minimize the maximum temperature level attained within the evacuated bottle during continuous passage of current therein. The use of this invention is especially applicable to continuous current ratings of vacuum interrupters that are 3000 A. or more. It should be pointed out that higher continuous ratings of vacuum interrupters are now limited since the diameter of the moving stem is limited. Larger stem diameters are undesirable because of the increased mass that has to be accelerated by the operating mechanism and also because the bellows would be increased in diameter which would increase cost. The heat pipe offers increased current rating without increasing mass or bellows diameter.